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Category Archives: Configuration

Where do I find the wwn of a disk in Windows / HyperV? That’s the question.

There are a number of identifiers to find out which LUN is which disk, but the only undeniably unique number to find out which disk is which LUN is by using the globally unique wwn number of a LUN. The question is: “where can I find the wwn of a disk in HyperV?”

The LUN number, as assigned by the storage array can be found by using diskpart:

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In the Unity the naa numbers (wwn) are listed in the “block” section, but not in the VMware section. If you view the LUNs from the host perspective, the naa numbers are visible, but in the list of LUNs would have been easier. You can list all details from LUNs and datastores on the CLI by using the uemcli commands:

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LUN-replication on Unity works slightly different than it previously did on VNX or even Clariion. In these older generations, when you deleted the mirrorview Mirror Group, both the primary and secondary LUNs became usable as separate entities.

In Unity the secondary LUN is a different beast. First of all: in Unity you can only set up replication from the primary Unity/LUN. The process on the source-Unity will create a LUN-replica and a replication session on both Unitys.

But what happens when you need hosts to access the secondary LUN? A failover works as designed and the previous secondary LUN becomes writable, but when you break the replication session, the replica-LUN has a flag that needs to be reset, but you’ll need the CLI to do that. This is how I did it:

In Unisphere I listed all LUNs and I made sure to include the “CLI ID” column

I noticed the ID of the LUN I need to grant access to is “res_56”

I started PUTTY and made sure logging to a file was configured so I could easily browse / search the possibly large amount of data some commands can produce, especially “-detail” commands tend to be very explicit

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Once in a while you come across a storage system that cannot be managed through the GUI or you just want to script or use the CLI to perform management tasks on a VNX. Recently I came across an old VNX2 which GUI wasn’t responding the way I’d like, so I decided to use the CLI instead.

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When decommissioning a VNX, I recently forgot to remove the array from the existing domain. After the VNX was “unracked and unstacked” I saw my mistake and tried to remove it from the domain by using the “add/remove systems” in Unisphere, but the remove-button was grayed out. Even engineering mode didn’t help me.

There is another way to remove unwanted VNXs from a domain! You might have guessed it already, because it’s by using the command line!

First you’ll have to find out what existing VNX is the domain master. This can be done in Unisphere by looking up the current master. Click on “Domains” followed by “Select Domain Master”.

The outcome will show you the list of domain in the domain as well as the current master.

Now you can open a command line box and enter the following command to deleted the unwanted VNX from the domain:

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Attaching multiple LUNs to a Windows host and later trying to figure out which LUN is which can be a drag. I found out that using the “details disk” command in diskpart can help you finding backup the right LUN:

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When formatting a newly added disk (LUN) to Hyper-V, often you’ll notice the formatting takes forever. Dell EMC therefore advises to disable VAAI on VMware hosts for the same issue, however modern VMware hosts don’t seem to have this problem. Hyper-V however still have this issue. To disable the UNMAP / TRIM from happening, use the following command:

fsutil behavior set DisableDeleteNotify 1

After formatting was performed, you’ll need to re-enable UNMAP / TRIM by issuing the following command:

Brocade Data Collection

There are 2 types of Data Collection associated with Brocade switches, “supportshow” and “supportsave”.

If the problem is related to basic “port issues”, a “supportshow” is sufficient. However, a more complex problem that involves Zoning, Performance, Reboots, CP Failovers, Fabric wide problems etc, requires a “SupportSave” type of collection. If the problem is multiswitch related (ISL connections, long distance configurations etc.) we need the supportsave from all relevant switches in the fabric.

The amount and type of information displayed in a supportshow output is depending on the type of switch as well as the collection options enabled in the switch configuration. This can be configured with the “supportshowcfgenable [option]” and “supportshowcfgdisable [option]”.

The output from the “supportshowcfgshow” command shows which subscripts will be enabled. The default groups are always enabled. Only on special occasions you will be asked to enable additional groups if necessary.

Performance and Intermittent Error Related Issues

If there is no sign of any obvious physical issue there might be link related problems which can identify performance problems and/or protocol related errors. Brocade counters are cumulative and keep doing so until a certain counter wraps, a switch reboots or the statistics are manually cleared.

Storage vendors for example require in these circumstances that a new baseline is created, a certain run-time has been achieved and separate commands are submitted against the suspected switch or switches.

To create a new baseline with cleared counters do the following:

Log in to the switch via Telnet or SSH

Submit the “statsclear” command

Submit the “slotstatsclear” command

After the agreed (mostly around one hour) run-time capture a new supportsave and upload this to the vendor’s service request.

SupportSave Data Collection (CLI Method)

When the problem is more sophisticated a supportsave from the switch is required. The supportsave command is available as of Fabric OS version 4.4 however, Fabric OS versions (> 6.2.x) provide a significant better collection of logs which represent the status overview of the switch and fabric. If you have a director class switch with two CP’s and/or core plus function blades it will also collect information from all the blades.

The supportsave will upload between 25 and 80 files depending on platform, Fabric OS level and enabled features to an FTP or SCP server. These will not be tarred or zipped into one file so it is important you create such an archive with a meaningful name. (ie. switchname-domainid-fabricid.zip)

Example

This command collects RASLOG, TRACE, supportShow, core file, FFDC data and then transfer them to a FTP/SCP server or a USB device. You could also simply type the “supportsave” command without any parameters and you will be asked for the extra information before the command is actually executed. The operation will usually take several minutes to complete.
NOTE: supportSave will transfer existing trace dump file first, then automatically generate and transfer latest one. There will be two trace dump files transferred after this command.

What is the Principal switch in a Brocade SAN

Principal switches maintain unique domain ID across the fabric. Principal switch ensures that each switch in a SAN have different domain ID. Any ISL of a switch that takes to the Principal switch is a upstream. Any ISL of a switch that goes away from principle switch is a downstream. All non principal switches are called subordinate switch. Zoning updated in a principal switch or a non principal switch will update zoning across the fabric. “date” command will be a read-only if a switch is configured with a Time server – NTP. Principal switch will update the time in all the non principal switches. tsclockserver is the command used to associate a switch to a NTP time server.

To manually set a subordinate switch to a principal switch use “fabricprincipal” command.

To elect a new principal switch:

>fabricprincipal -1 # This command will see the appropriate principal switch and make it as a new principal switch. Also, this will elect new upstream and downstream ISLs

To force a switch to be a principal switch:

> fabricprincipal -f # This command will force the switch to be the principal switch of the fabric. This will also elect new upstream and downstream ISLs

To see the current settings:

> fabricprincipal -q # This command will query the current settings and displays

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How do I configure Cisco DCNM so Putty starts when I select to go to the command line of a switch?

If you right click on a switch in the overview section in DCNM, you can go to the command line of that switch, but how do you change the default CLI SSH into Putty (or another telnet / SSH capable tool)?

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DCNM is down. I love the tool, but the downside is that you forget how to use the CLI. I faced downtime of our DCNM appliance and was forced to use the CLI instead. No big deal actually, but I still want to post the commands to use when you need to add new hosts to existing zones.

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Over the years I collected a number of useful CLI commands to control the DMX / VMAX machines I worked with. Even though nowadays Unisphere for VMAX is a useful tool, nothing really beats the command line!Read more »

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Creating tdevs and masking them to hosts (storage groups in a masking view) is relatively easy in the Unisphere for VMAX interface, but what if you add a few tdevs of exactly the same size and you want to make sure that the VMware administrator uses the right LUN for each VMFS he’s going to create? One way to make sure he knows which LUN corresponds with what tdev is the Host LUN id. To list the host LUN ids

symaccess -sid 1234 show view mv_some-maskingview-name

or (a bit more verbose)

symaccess -sid 1234 list view -name mv_some-maskingview-name -detail

The second command shows each initiator group nested within other initiator groups as well.

Both generate a table with the following headers:

Sym Host
Dev Dir:Port Physical Device Name Lun Attr Cap(MB)

The column under “Host Lun” shows the Host LUN ids.

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Recently I needed to make some edits on vmdk files in order to get rid of a reference to the change tracking files, as mentioned in Gabrie’s post: Cannot open the disk and could not open change tracking file. An SSH connection to a VMware ESXi host was required. SHH was disabled and I needed to enable it temporarily.

How to enable SSH on an ESXi host using the vSphere client

In vSphere, select the host you want to enable SSH on.

Select the “Configuration” TAB, then “Security Profile”. In the upper right select “Properties.

A new window opens, now select SSH (you may need to scroll down a bit) and in the lower right select “Options”.

Again a new window opens and here you can either “Start” or “Stop” the SSH daemon.

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Sometimes you just want to run a VNX, Avamar, PowerPath, Data Domain or Isilon as a virtual machine to see how things work, or to write work instructions. And EMC offers a lot of these virtual appliances for free!

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Smart zoning examples

In my smart zoning post from last February I already presented the way to get started with Cisco smart zoning. I initially planned to give a more detailed calculation on how much time you can save if you were using smart zoning compared to SIST zoning.

I was talking to an EMC SAN instructor (Richard Butler) this week and after I did a little white boarding and used my hands to picture how massive a traditional SIST zone environment would be, we agreed smart zoning is the way to go.

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The published content is not approved or even read in advance by any vendor and does not necessarily reflect opinions of this vendor. This is my blog, not a vendor blog.

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